[MaterialSwitch] Support for processing state

Is your feature request related to a problem? Please describe.

Support processing state drawable for thumb as suggested in material docs. This helps with business logic where a request can't be processed immediately and has some user noticeable latency like network requests.

Describe the solution you'd like

API to specify processing state drawable (to be drawn over thumb). It would be nice to support default processing drawable.
API to indicate processing state when calling setChecked for both on and off states

setChecked(true, true) -> On state and loading
setChecked(true, false) -> On state
setChecked(false, true) -> Off state and loading
setChecked(false, false) -> Off state

Describe alternatives you've considered

Additional context

https://user-images.githubusercontent.com/1020585/234715458-f114e73e-0d1a-41c8-93d8-01247c6ae01a.mov

We also happily accept pull requests.

Beginne bei der MaterialSwitch-Komponente und ihrem bestehenden setChecked-Einstiegspunkt und verfolge anschließend, wie das Thumb-Drawable und Änderungen des Checked-Zustands behandelt werden. Definiere das Verarbeitungs-Drawable und das Ladeverhalten für die vier im Issue beschriebenen setChecked-Kombinationen und bewahre dabei die normalen Ein- und Aus-Visualisierungen.